.TH zzuf 1 "2015-01-06" "zzuf @PACKAGE_VERSION@"
.SH NAME
zzuf \- multiple purpose fuzzer
.SH SYNOPSIS
\fBzzuf\fR [\fB\-AcdimnqSvxX\fR]
[\fB\-s\fR \fIseed\fR|\fB\-s\fR \fIstart:stop\fR]
[\fB\-r\fR \fIratio\fR|\fB\-r\fR \fImin:max\fR]
[\fB\-f\fR \fIfuzzing\fR] [\fB\-D\fR \fIdelay\fR] [\fB\-j\fR \fIjobs\fR]
[\fB\-C\fR \fIcrashes\fR] [\fB\-B\fR \fIbytes\fR] [\fB\-t\fR \fIseconds\fR]
[\fB\-T\fR \fIseconds\fR] [\fB\-U\fR \fIseconds\fR] [\fB\-M\fR \fImebibytes\fR]
[\fB\-b\fR \fIranges\fR] [\fB\-p\fR \fIports\fR] [\fB\-P\fR \fIprotect\fR]
[\fB\-R\fR \fIrefuse\fR] [\fB\-a\fR \fIlist\fR] [\fB\-l\fR \fIlist\fR]
[\fB\-I\fR \fIinclude\fR] [\fB\-E\fR \fIexclude\fR] [\fB\-O\fR \fIopmode\fR]
[\fIPROGRAM\fR [\fIARGS\fR]...]
.br
\fBzzuf \-h\fR | \fB\-\-help\fR
.br
\fBzzuf \-V\fR | \fB\-\-version\fR
.SH DESCRIPTION
.PP
\fBzzuf\fR is a transparent application input fuzzer. It works by intercepting
file and network operations and changing random bits in the program's input.
\fBzzuf\fR's behaviour is deterministic, making it easy to reproduce bugs.
.SH USAGE
.PP
\fBzzuf\fR will run an application specified on its command line, one or
several times, with optional arguments, and will report the application's
relevant behaviour on the standard error channel, eg:
.PP
\fB    zzuf cat /dev/zero\fR
.PP
Flags found after the application name are considered arguments for the
application, not for \fBzzuf\fR. For instance, \fB\-v\fR below is an
argument for \fBcat\fR:
.PP
\fB    zzuf \-B 1000 cat \-v /dev/zero\fR
.PP
When no program is specified, \fBzzuf\fR simply fuzzes the standard input, as
if the \fBcat\fR utility had been called:
.PP
\fB    zzuf < /dev/zero\fR
.SH OPTIONS
.SS "Generic program information"
.TP
\fB\-h\fR, \fB\-\-help\fR
Display a short help message and exit.
.TP
\fB\-V\fR, \fB\-\-version\fR
Output version information and exit.
.SS "Operating mode"
.TP
\fB\-f\fR, \fB\-\-fuzzing\fR=\fImode\fR
Select how the input is fuzzed. Valid values for \fImode\fR are:
.RS
.TP
\fBxor\fR
randomly set and unset bits
.TP
\fBset\fR
only set bits
.TP
\fBunset\fR
only unset bits
.RE
.IP
The default value for \fImode\fR is \fBxor\fR.
.TP
\fB\-O\fR, \fB\-\-opmode\fR=\fImode\fR
Use operating mode \fImode\fR. Valid values for \fImode\fR are:
.RS
.TP
\fBpreload\fR
override functions by preloading libzzuf into the executable using the
system's dynamic linker
.TP
\fBcopy\fR
temporarily copy files that need to be fuzzed
.RE
.IP
The default value for \fImode\fR is \fBpreload\fR. \fBcopy\fR is useful on
platforms that do not support dynamic linker injection, for instance when
fuzzing a Cocoa application on Mac OS X.
.TP
\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
.PD 0
.TP
\fB\-s\fR, \fB\-\-seed\fR=\fIstart:\fR
.PD 0
.TP
\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
.PD
Specify the random seed to use for fuzzing, or a range of random seeds.
Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
the same way, even with a different target application. The purpose of this is
to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
causes the target application to crash.

If a range is specified, \fBzzuf\fR will run the application several times,
each time with a different seed, and report the behaviour of each run. If no
\(oqstop\(cq is specified after \(oq:\(cq, \fBzzuf\fR will increment the seed
value indefinitely.
.TP
\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
.PD 0
.TP
\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
.PD
Specify the proportion of bits that will be randomly fuzzed. A value of 0
will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
the input files undiscernible from random data. The default fuzzing ratio
is 0.004 (fuzz 0.4% of the files' bits).

A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
values from the interval. The choice is deterministic and only depends on
the interval bounds and the current seed.
.TP
\fB\-A\fR, \fB\-\-autoinc\fR
Increment random seed each time a new file is opened. This is only required
if one instance of the application is expected to open the same file several
times and you want to test a different seed each time.
.SS "Output"
.TP
\fB\-d\fR, \fB\-\-debug\fR
Activate the display of debug messages. Can be specified multiple times for
increased verbosity.
.TP
\fB\-q\fR, \fB\-\-quiet\fR
Hide the output of the fuzzed application. This is useful if the application
is very verbose but only its exit code or signaled status is really useful to
you.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
Print information during the run, such as the current seed, what processes
get run, their exit status, etc.
.TP
\fB\-m\fR, \fB\-\-md5\fR
Instead of displaying the program's \fIstandard output\fR, just print its MD5
digest to \fBzzuf\fR's standard output. The standard error channel is left
untouched. See also the \fB\-X\fR flag.
.TP
\fB\-X\fR, \fB\-\-hex\fR
Convert the fuzzed program's \fIstandard output\fR to hexadecimal. The standard
error channel is left untouched. See also the \fB\-m\fR flag.
.SS "Process control"
.TP
\fB\-B\fR, \fB\-\-max\-bytes\fR=\fIn\fR
Automatically stop after \fIn\fR bytes have been output.

This either terminates child processes that output more than \fIn\fR bytes
on the standard output and standard error channels, or stop reading from
standard input if no program is being fuzzed.

This is useful to detect infinite loops. See also the \fB\-U\fR and \fB\-T\fR
flags.
.TP
\fB\-C\fR, \fB\-\-max\-crashes\fR=\fIn\fR
Stop forking when at least \fIn\fR children have crashed. The default value
is 1, meaning \fBzzuf\fR will stop as soon as one child has crashed. A value
of 0 tells \fBzzuf\fR to never stop.

Note that \fBzzuf\fR will not kill any remaining children once \fIn\fR is
reached. To ensure that processes do not last forever, see the \fB\-U\fR
flag.

A process is considered to have crashed if any signal (such as, but not limited
to, \fBSIGSEGV\fR) caused it to exit. If the \fB\-x\fR flag is used, this will
also include processes that exit with a non-zero status.

This option is only relevant if the \fB\-s\fR flag is used with a range
argument. See also the \fB\-t\fR flag.
.TP
\fB\-D\fR, \fB\-\-delay\fR=\fIdelay\fR
Do not launch more than one process every \fIdelay\fR seconds. This option
should be used together with \fB\-j\fR to avoid fork bombs.
.TP
\fB\-j\fR, \fB\-\-jobs\fR=\fIjobs\fR
Specify the number of simultaneous children that can be run. By default,
\fBzzuf\fR only launches one process at a time.

This option is only relevant if the \fB\-s\fR flag is used with a range
argument. See also the \fB\-D\fR flag.
.TP
\fB\-M\fR, \fB\-\-max\-memory\fR=\fImebibytes\fR
Specify the maximum amount of memory, in mebibytes (1 MiB = 1,048,576 bytes),
that children are allowed to allocate. This is useful to detect infinite loops
that eat up a lot of memory.

The value should be set reasonably high so as not to interfer with normal
program operation. By default, it is set to 1024 MiB in order to avoid
accidental excessive swapping. To disable the limitation, set the maximum
memory usage to -1 instead.

\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
relies on the operating system's ability to enforce such limitations.
.TP
\fB\-S\fR, \fB\-\-signal\fR
Prevent children from installing signal handlers for signals that usually
cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
simply crash. If you do not want core dumps, you should set appropriate limits
with the \fBlimit coredumpsize\fR command. See your shell's documentation on
how to set such limits.
.TP
\fB\-t\fR, \fB\-\-max\-time\fR=\fIn\fR
Stop forking after \fIn\fR seconds. By default, \fBzzuf\fR runs until the
end of the seed range is reached.

Note that \fBzzuf\fR will not kill any remaining children once \fIn\fR is
reached. To ensure that processes do not last forever, see the \fB\-U\fR
flag.

This option is only relevant if the \fB\-s\fR flag is used with a range
argument. See also the \fB\-C\fR flag.
.TP
\fB\-T\fR, \fB\-\-max\-cputime\fR=\fIn\fR
Automatically terminate child processes that use more than \fIn\fR seconds
of CPU time.

\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
relies on the operating system's ability to enforce such limitations. If the
system sends \fBSIGXCPU\fR signals and the application catches that signal,
it will receive a \fBSIGKILL\fR signal after 5 seconds.

This is more accurate than \fB\-U\fR because the behaviour should be
independent from the system load, but it does not detect processes stuck into
infinite \fBselect\fR() calls because they use very little CPU time. See also
the \fB\-B\fR and \fB\-U\fR flags.
.TP
\fB\-U\fR, \fB\-\-max\-usertime\fR=\fIn\fR
Automatically terminate child processes that run for more than \fIn\fR
seconds. This is useful to detect infinite loops or processes stuck in other
situations. See also the \fB\-B\fR and \fB\-T\fR flags.
.TP
\fB\-x\fR, \fB\-\-check\-exit\fR
Report processes that exit with a non-zero status. By default only processes
that crash due to a signal are reported.
.SS "Filtering"
.TP
\fB\-a\fR, \fB\-\-allow\fR=\fIlist\fR
Only fuzz network input for IPs in \fIlist\fR, a comma-separated list of
IP addresses. If the list starts with \fB!\fR, the flag meaning is reversed
and all addresses are fuzzed except the ones in the list.

As of now, this flag only understands INET (IPv4) addresses.

This option requires network fuzzing to be activated using \fB\-n\fR.
.TP
\fB\-b\fR, \fB\-\-bytes\fR=\fIranges\fR
Restrict fuzzing to bytes whose offsets in the file are within \fIranges\fR.

Range values start at zero and are inclusive. Use dashes between range values
and commas between ranges. If the right-hand part of a range is ommited, it
means end of file. For instance, to restrict fuzzing to bytes 0, 3, 4, 5 and
all bytes after offset 31, use \(oq\fB\-b0,3\-5,31\-\fR\(cq.

This option is useful to preserve file headers or corrupt only a specific
portion of a file.
.TP
\fB\-c\fR, \fB\-\-cmdline\fR
Only fuzz files whose name is specified in the target application's command
line. This is mostly a shortcut to avoid specifying the argument twice:

\fB    zzuf \-c cat file.txt\fR

has the same effect as

\fB    zzuf \-I \(aq^file\\.txt$\(aq cat file.txt\fR

See the \fB\-I\fR flag for more information on restricting fuzzing to
specific files.
.TP
\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
Do not fuzz files whose name matches the \fIregex\fR regular expression. This
option supersedes anything that is specified by the \fB\-I\fR flag. Use this
for instance if you are unsure of what files your application is going to read
and do not want it to fuzz files in the \fB/etc\fR directory.

Multiple \fB\-E\fR flags can be specified, in which case files matching any one
of the regular expressions will be ignored.
.TP
\fB\-i\fR, \fB\-\-stdin\fR
Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
.TP
\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
Only fuzz files whose name matches the \fIregex\fR regular expression. Use
this for instance if your application reads configuration files at startup
and you only want specific files to be fuzzed.

Multiple \fB\-I\fR flags can be specified, in which case files matching any one
of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
.TP
\fB\-l\fR, \fB\-\-list\fR=\fIlist\fR
Cherry-pick the list of file descriptors that get fuzzed. The Nth descriptor
will really be fuzzed only if N is in \fIlist\fR.

Values start at 1 and ranges are inclusive. Use dashes between values and
commas between ranges. If the right-hand part of a range is ommited, it means
all subsequent file descriptors. For instance, to restrict fuzzing to the
first opened descriptor and all descriptors starting from the 10th, use
\(oq\fB\-l1,10\-\fR\(cq.

Note that this option only affects file descriptors that would otherwise be
fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
program, only the next descriptor with a read flag will be the first one
considered by the \fB\-l\fR flag.
.TP
\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
Protect a list of characters so that if they appear in input data that would
normally be fuzzed, they are left unmodified instead.

Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
The sequences interpreted by \fBzzuf\fR are:
.RS
.TP
\fB\\n\fR
new line
.TP
\fB\\r\fR
return
.TP
\fB\\t\fR
tabulation
.TP
\fB\\\fR\fINNN\fR
the byte whose octal value is \fINNN\fR
.TP
\fB\\x\fR\fINN\fR
the byte whose hexadecimal value is \fINN\fR
.TP
\fB\\\\\fR
backslash (\(oq\\\(cq)
.RE
.IP
You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(aq\\001\-/\(aq\fR\(cq.

The statistical outcome of this option should not be overlooked: if characters
are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
on the data being fuzzed. For instance, asking to fuzz 1% of input bits
(\fB\-r0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
result in an actual average fuzzing ratio of 0.9% with truly random data,
0.3% with random ASCII data and 0.2% with standard English text.

See also the \fB\-R\fR flag.
.TP
\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
Refuse a list of characters by not fuzzing bytes that would otherwise be
changed to a character that is in \fIlist\fR. This does not prevent characters
from appearing in the output if the original byte was already in \fIlist\fR.

See the \fB\-P\fR option for a description of \fIlist\fR.
.SS "Network"
.TP
\fB\-n\fR, \fB\-\-network\fR
Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.

Only INET (IPv4) and INET6 (IPv6) connections are fuzzed. Other protocol
families are not yet supported.
.TP
\fB\-p\fR, \fB\-\-ports\fR=\fIranges\fR
Only fuzz network ports that are in \fIranges\fR. By default \fBzzuf\fR
fuzzes all ports. The port considered is the listening port if the socket
is listening and the destination port if the socket is connecting, because
most of the time the source port cannot be predicted.

Range values start at zero and are inclusive. Use dashes between range values
and commas between ranges. If the right-hand part of a range is ommited, it
means end of file. For instance, to restrict fuzzing to the HTTP and HTTPS
ports and to all unprivileged ports, use \(oq\fB\-p80,443,1024\-\fR\(cq.

This option requires network fuzzing to be activated using \fB\-n\fR.
.SH DIAGNOSTICS
.PP
Exit status is zero if no child process crashed. If one or several children
crashed, \fBzzuf\fR exits with status 1.
.SH EXAMPLES
.PP
Fuzz the input of the \fBcat\fR program using default settings:
.PP
\fB    zzuf cat /etc/motd\fR
.PP
Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
.PP
\fB    zzuf \-s94324 \-r0.01 cat /etc/motd\fR
.PP
Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
and prevent non-ASCII characters from appearing in the output:
.PP
\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
.PP
Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
original input and excluding \fB.xml\fR files from fuzzing (because
\fBconvert\fR will also open its own XML configuration files and we do not
want \fBzzuf\fR to fuzz them):
.PP
\fB    zzuf \-E \(aq\\.xml$\(aq convert foo.jpeg \-format tga /dev/null\fR
.PP
Fuzz the input of VLC, using file \fBmovie.avi\fR as the original input
and restricting fuzzing to filenames that appear on the command line
(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
can be read by VLC to reproduce the same behaviour without using
\fBzzuf\fR:
.PP
\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
.br
\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
.br
\fB    vlc fuzzy\-movie.avi\fR
.PP
Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
standard output messages (\fB\-q\fR), launching up to five simultaneous child
processes (\fB\-j5\fR) but waiting at least half a second between launches
(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
(\fB\-S\fR):
.PP
\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-j5 \-D0.5 \-T60 \-S \\\fR
.br
\fB      mplayer \-benchmark \-vo null \-fps 1000 movie.avi\fR
.PP
A more advanced VLC fuzzing example, stopping only at the first crash:
.PP
\fB    zzuf \-j4 \-vqc \-r0.000001:0.01 \-s0: vlc \-v \-I dummy movie.avi \\\fR
.br
\fB       \-\-sout \(aq#transcode{acodec=s16l,vcodec=I420}:dummy\(aq vlc:quit
.PP
Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
.PP
\fB    seq \-f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
.br
      (or: \fBjot \-w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
.br
\fB    zzuf \-A \-I \(aqhello[.]jpg\(aq \-r0.001 firefox hello.html\fR
.PP
Run a simple HTTP redirector on the local host using \fBsocat\fR and
corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
after one megabyte of data was received on it (\fB\-b1000000\-\fR):
.PP
\fB     zzuf \-n \-A \-b1000000\- \\\fR
\fB       socat TCP4\-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
.PP
Browse the intarweb (\fB\-n\fR) using Firefox\(tm without fuzzing local files
(\fB\-E.\fR) or non-HTTP connections (\fB\-p80,8010,8080\fR), preserving
the beginning of the data sent with each HTTP response (\fB\-b4000\-\fR)
and using another seed on each connection (\fB\-A\fR):
.PP
\fB    zzuf \-r 0.0001 \-n \-E. \-p80,8010,8080 \-b4000\- \-A firefox\fR
.SH RESTRICTIONS
.PP
Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
processes, it will fail in the presence of any mechanism that disables
preloading. For instance setuid root binaries will not be fuzzed when run
as an unprivileged user.
.PP
For the same reasons, \fBzzuf\fR will also not work with statically linked
binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
.PP
Though best efforts are made, identical behaviour for different versions of
\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
different operating systems and with different target programs is only
guaranteed when the same version of \fBzzuf\fR is being used.
.SH BUGS
.PP
\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
.PP
It is not yet possible to insert or drop bytes from the input, to fuzz
according to the file format, to swap bytes, etc. More advanced fuzzing
methods are planned.
.PP
As of now, \fBzzuf\fR does not really support multithreaded applications. The
behaviour with multithreaded applications where more than one thread does file
descriptor operations is undefined.
.SH HISTORY
.PP
\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
multimedia stream corrupter used to find bugs in the VLC media player.
.SH SEE ALSO
.PP
\fBlibzzuf(3)\fR, \fBzzat(1)\fR
.SH AUTHOR
.PP
Copyright \(co 2002\-2015 Sam Hocevar <sam@hocevar.net>.
.PP
\fBzzuf\fR and this manual page are free software. They come without any
warranty, to the extent permitted by applicable law. You can redistribute
them and/or modify them under the terms of the Do What the Fuck You Want
to Public License, Version 2, as published by the WTFPL Task Force. See
\fBhttp://www.wtfpl.net/\fR for more details.
.PP
\fBzzuf\fR's webpage can be found at \fBhttp://caca.zoy.org/wiki/zzuf\fR.
An overview of the architecture and inner works is at
\fBhttp://caca.zoy.org/wiki/zzuf/internals\fR.
